This is how I configure my Apache LogFormat. This includes a lot of extra info that a high-traffic site might not want to log, but I found Apache's logging facility to be very efficient. The extra log info has a very log overhead. This configuration eliminates log messages from favicon.ico requests; server status checks (libwww-perl); and internal connection checks (internal dummy connection).

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This is how I configure my Apache LogFormat.

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This includes the process ID of the child that serviced a request and the time taken. This is useful in debugging PHP scripts.

This includes a lot of extra info that a high-traffic site might not want to log, but I found Apache's logging facility to be very efficient. The extra log info has low overhead.

# %V The server name according to the UseCanonicalName setting. Useful for virtual hosting servers.
# %h Remote host
# %l Remote logname (from identd, if supplied). This will return a dash unless mod_ident is present and IdentityCheck is set On.
# %u Remote user (from auth; may be bogus if return status (%s) is 401)
# %t Time the request was received (standard English format)
# %r First line of request
# %>s status. For requests that got internally redirected, this is the status of the *original* request --- %>s for the last.
# %b Size of response in bytes, excluding HTTP headers. In CLF format, i.e. a '-' rather than a 0 when no bytes are sent.
# %{Referer}i The contents of Foobar: header line(s) in the request sent to the server.
# %{User-Agent}i
# %{Foorbar}C The contents of cookie Foobar in the request sent to the server.
# %P The process ID of the child that serviced the request.
# %D The microseconds of time taken to serve the request.
LogFormat "%V %h %l %u %t \"%r\" %>s %b \"%{Referer}i\" \"%{User-Agent}i\" %P %D" vcombinedwithPD
SetEnvIf Request_URI "^/favicon\.ico$" dontlog
SetEnvIf User-Agent "libwww-perl.*" dontlog
SetEnvIf User-Agent ".*internal dummy connection.*" dontlog
CustomLog logs/access_log vcombinedwithPD env=!dontlog